The high-speed transmission of signal has been reaching a limitation of operation speed of electrical circuit. Thus, it is difficult to further increase the velocity of transmitted signal. Currently, a next-generation ultra-high-speed and large-capacity communication means using an optical signal processing technique where an optical signal is processed as it is has been researched at some research institutions.
Also, as an effective one of the next-generation ultra-high-speed and large-capacity communication means, an optical time-division multiplexing system, where an optical pulse signal is generated by intensity-modulating short-pulse light with a very short pulse width and an optical time-division-multiplexed signal for ultra-high-speed and large-capacity communication is produced by multiplexing several optical pulse signals while giving a bit of time difference, has been researched.
However, in the conventional optical transmitter and optical receiver for optical time-division multiplexing transmission, means for identifying each channel in order to extract the optical pulse signal of each channel from the optical time-division-multiplexed signal transmitted to the optical receiver is not discussed. Namely, at present, only means for conducting the optical time-division multiplexing and demultiplexing are mainly researched and means for conducting the channel selection is not suggested.
This is because, at present, only the optical time-division multiplexing system with means for achieving main functions as the next-generation optical communication system has been researched and the research does not reach a stage to discuss the system after achieving the main functions.